O1 component of geomagnetic lunar daily variation at alibag and its contamination by M2 component.

Abstract

An analysis of absolute mean hourly values of the three geomagnetic elements H, D and Z at Alibag for the period 1932-1972 has revealed clear and significant L(O1), the geomagnetic lunar daily variation associated with the lunar atmospheric tide 01. Partial tides are small in comparison with the phase law tides, suggesting that the variation resulting from the atmospheric tide O1 and higher harmonics of ionospheric conductivity contribute little to L(O1) at Alibag. Separation of L(O1) into parts of oceanic and ionospheric origin shows that (i) primary source of L(O1) in Z is the oceanic dynamo; (ii) smaller amplitude of the first harmonic of L(O1) compared to that of the second, contrary to expectation, is not due to the influence of oceanic dynamo contribution on L(O1). It is inferred that even yearly L(O1) contains some contribution from L(M2), lunar variation associated with the atmospheric tide M2. Next, by applying the formulae due to Winch, the seasonal harmonics of L(O1) and L(M2) are corrected for the possible contamination of one by the other. It is found that seasonal progression of L(O1) and L(M2) prior to and after the removal of the effect of one from the other remains the same.

Quasi‐Diurnal Lunar Tide O1 in Ionospheric Total Electron Content at Solar Minimum

“…In the following discussion, we prefer the first case of interpretation, that an O 1 tide is generated in the lower atmosphere and amplified during its ascent to the upper atmosphere. Previous studies about the O 1 tide are mainly based on the geomagnetic lunar O 1 component (Arora, 1979; Rao & Sastri, 1974; Winch, 1970). However, these studies were usually at a few locations with ground magnetometers.…”

“…Malin (1970) described how the ionospheric and oceanic contributions to the geomagnetic lunar tides can be separated and that both sources generate important contributions to the ground magnetometer measurements. Significant contributions of the atmospheric O 1 tide (via the ionospheric dynamo) were derived from ground magnetometer data in several studies in the 1970s (Arora, 1979; Rao & Sastri, 1974; Winch, 1970).…”